1. Field of the Invention
The present invention relates to a pressurized fluid system, and, more particularly, to a valve assembly for controlling a discharge of a pressurized fluid using a poppet.
2. Description of the Related Art
Poppet valves are used in various aerospace applications, such as gas turbine engines, rocket engines, thrusters, aerospace vehicle fuel, environmental, and cooling systems, hydraulic and pneumatic systems, and various other aerospace vehicle systems. A poppet valve may be used as a pressure regulator, a relief valve, or a bleed valve. Poppet valves include a poppet that is used to control flow through the valve or pressure at the valve assembly's inlet port or discharge port, and may also include a piston for operating or assisting to operate the poppet. The poppet controls the flow by moving closer to or further from a valve seat, and can engage and contact the valve seat in order to selectively regulate, allow, or disallow flow through the valve. Preferably, the valve is actuated by the static pressure of the fluid exposed to or passing through the valve.
In a pressure regulator, the valve is used to regulate pressure or flow from a pressurized source in order to control the pressure or flow to or through some device. The regulator valve is normally open, allowing fluid to flow through the valve, with the flow rate and pressure dependent upon the pressure at the valve's discharge port and/or some reference pressure.
Generally, during the operation of a typical valve, especially at high pressure ratios across the valve, the flow of fluid has a high velocity, yielding high dynamic pressure components, otherwise known as velocity head components, especially in vicinity of the poppet seal and valve seat that are located in the primary flowpath through the valve, and are immersed in and contact and valve/regulate the flow through the valve primary flowpath (as opposed to the piston, for example, which, although it controls or helps to control the poppet position, it is not in the primary flowpath, and does not itself contact or valve or regulate the flow). The dynamic pressure components of the flow acting on the poppet cause changes in the pressure distribution on the poppet's operative pressure-acting faces, effecting skewed results and/or measurable inaccuracies in the regulation of pressure or flow through the valve. In addition, high dynamic pressure components can change the force balance internal to the valve, i.e., by acting on the poppet in addition to or in contravention to the intended action of the fluid's static pressure acting on the poppet, thus requiring additional force to open or close the valve and causing hysteresis, depending on the flow rate.
These adverse effects are exaggerated when high flow rates are involved, yielding a dynamic pressure component approaching fifty percent of the pressurized source's total pressure.
What is needed in the art is valve that is configured such that the poppet is isolated from the dynamic pressure or velocity head components of the flow stream passing through the valve to thereby eliminate the adverse effects associated with the dynamic pressure components of flow through the valve.